As is known, in a bicycle the height and the back setting of the saddle are values which are strictly related to each other, to the extent that the modification of one determines a variation of the other.
The height of the saddle is the distance between the center of central movement and the anatomic center of the saddle which is situation 12 centimeters from the rear part of the saddle.
The back setting of the saddle consists of the distance between the vertical from the center of central movement and the saddle.
Such a distance is normally measured with respect to the anatomic center of the saddle (conventionally a point 12 cm from the rear part).
As already pointed out, therefore, these two parameters are strictly correlated: by raising the saddle there is also an increase in the back setting (which can be measured at about 3 millimeters on frames with the shaft at 73° and at about 2.5 millimeters on frames with the shaft at 75°). By lowering the saddle there is a reduction in the back setting (values equal to the previous ones, but negative). By reducing the back setting there is a decrease in the saddle height (about 2.5 millimeters for each centimeter displacement forward). By increasing the back setting of the saddle there is an increase in the saddle height (by about 2.5 millimeters for each centimeter displacement backward).
According to such a strict connection between these two parameters, there can be saddle positions with equal height values but with different back settings, or equal back setting with different heights.
Due to the above, the height and back setting of the saddle must be such as to allow the legs to maximize their drive and recovery potential on the pedal and must allow an effective and synergic intervention of all of the leg muscles.
It is also known to use absorbing devices on a bicycle which can be subdivided into two main groups.
The first group concerns shock-absorber devices made during the production of the bicycle.
Amongst these devices there are, for example, shock-absorbers defined by front and/or rear forks which are telescopic or oscillating.
The second group includes accessory shock-absorber devices, i.e. those devices which can sometimes be applied on a bicycle which has already been finished to improve its performance.
Amongst these devices there are those using springs applied to the saddle or handlebar post.
As is easy to understand, the first group of devices is fixed to the bicycle on which it is made limiting the user's freedom of choice.
Moreover, devices of both the first and second group can be heavy, which is unthinkable for a cyclist, complex and expensive.
Besides these drawbacks which are already harmful in themselves, it should be highlighted that, above all in the case of shock-absorber devices for the saddle which determine a displacement thereof along the axis of the post, the saddle frequently moves towards and away from the center of central movement, with all of the drawbacks described above and which are also unacceptable for any cyclist.